Thank you for your response. I successfully managed to config WAN port as a LAN port. However I'm totally out of ideas how to configure this WAN port as an isolated network from LAN1,LAN2,LAN3. I tried creating a new VLAN with ID 103. There I put WAN Tagged, all other Off. Then I did a new connection under Interfaces gave a different Static address for this VLAN. Then activated DHCP server. Then under Physical interfaces i tried eth0.103. Then clicked enable. The devices in this WAN port can connect to internet and also communicate with other devices on the network. When under VLAN I change WAN from Tagged to Untagged, it is not possible to connect to internet. I have read the Tagged and Untagged VLAN chapter under Rutx09 like a over 10 times. Tried different setting but I'm not able to isolate the networks from each other.
I would appreciate if someone could upload somekind example in how to configure the VLAN etc.